The black-throated loon is a migratory aquatic bird found in northern Europe and Asia. It winters along sheltered, ice-free coasts of the north-east Atlantic Ocean and the eastern and western Pacific Ocean. There are two subspecies: a viridigularis Gavia arctica and the black diverated gavia arcticus. The population of this loon has been declining, but it is still rated as least concern.
About Black-throated loon in brief
The black-throated loon is a migratory aquatic bird found in northern Europe and Asia. It winters along sheltered, ice-free coasts of the north-east Atlantic Ocean and the eastern and western Pacific Ocean. This loon was first described by Carl Linnaeus in 1758. It was previously considered to be the same species as the Pacific loon, of which it is traditionally considered to is a sister species. The population of this loon has been declining, but it is still rated as least concern by the International Union for the Conservation of Nature. There are two subspecies: a viridigularis Gavia arctica and the black diverated gavia arcticus. The name Gavia comes from the Latin for’sea mew’ as used by the ancient Roman naturalist Pliny the Elder. The subspecies G. a. viridIGularis stems from ‘green’ and ‘gularis’ meaning ‘the throat of the loon’, in reference to the black patch on the throat of its nominate subspecies. It is protected under both the Migratory Bird Treaty Act of 1918 and the Agreement on the conservation of African-Eurasian M migratory Waterbirds. It lays a clutch of two, rarely one or three, brown-green eggs with dark splotches. The chick hatches, and is fed a diet of small fish and invertebrates. To catch this food, it forages by itself or in pairs, very rarely foraging in groups. It dives from the water, going no deeper than 5 metres.
Most dives are successful. Whether or not at least one chick will hatch from a nest is variable, ranging from 30% to 90%. Most failures come from predators and flooding. The timing of the breeding season is variable; in the southern part of its range, this Loon starts breeding in April, whereas in the northern portion, it waits until after the spring thaw. It builds an oval-shaped nest that measures about 23 centimetres across, either near the breeding lake or on vegetation emerging from it. The juvenile is similar to the non-breeding adult, except more brown overall. It can weigh anywhere from 1. 3 to 3. 4 kilograms. In breeding plumage, the adult has mostly black upperparts, with the exception of some of the mantle and scapulars, which have white squares. The head and hindneck are grey, and the sides white and striped black. The underparts are mostly white, including the bottom of the throat. The flanks are also white, a feature which can be used to separate this bird from thePacific loon. When it is not breeding, the black patches on its throat are absent, replaced with white; most of the black lines on the throats are also missing, except those on the bottom sides, and upperparts are unpatterned with the exceptions of a few white spots on the upperwing.